Method of extinguishing fires and fluid used therein



Patented Nov. 27, 1945 UNITED STATES PATENT' OFFICE METHOD OF EXTINGUISHING FIRES AND FLUID USED THEREIN Lewis G. Morris Timpson, llalnfleld, N. J.

No Drawing. Application July 23, 1943,

Serial No. 495,952

6 Claims.

larly in working out a method of smothering and extinguishing forced-draft fires of the type exemplified by aircraft fires, and in compounding a composition for use in fire-fighting apparatus designed for extinguishing such fires. For the purpose of disclosure of the principles of'the'invention such an embodiment will be more particularly described, but it will be understood that the principles may be variously embodied as the requirements of particular uses demand.

Fire-fighting equipment and extinguishing agents for aircraft fires are subject to certain obvious special requirements. The agent and its container should be of as light weight as possible. Liquid compositions used should not freeze at the low temperatures to be met with and should not have too high a vapor pressure at the highest temperature of storage or of use. If the fireextinguishing liquid is to be shipped by ordinary freight the vapor pressure should be less than 25 pounds per square inch, gauge pressure, at '70 degrees F., to comply with I. C. C. Freight Tarifi Rule 4. The disagreeable and toxic effects should not be intolerable nor dangerous. The extinguishing agent is more effective if it acts quickly and if it smothers the fire.

The nature and objects of the invention will be better understood from a description ofa particular illustrative embodiment thereof. The method involves applying to the fire a gas or vapor in such manner that in part the flre will be smothered and in part the flame will be carried away and will not flash back to the combustible material. The invention provides an improved composition compounded to form an effective combination of gases' or vapors when suitably applied to a fire.

Compositions which have proved particularly These compositions will not freeze at 100 degrees below zero C. The proportions of the several ingredients, respectively, may vary considerably and diluting ingredients, or other active ingredients, may be added. Preferably the ethylbromide forms a major proportion of the effective ingredients and methylbromide and ethyleneclilorobromide constitute minor proportions.

Good fire-extinguishing action can be obtained if the principal active ingredients are present in the following preferred proportions relative to one another:

Per cent Ethylbromide 70 to 90 Methylbromide 5 to 10 Ethylenechlorobromide 5 to The foregoing proportions mentioned as preferred are not to be construed as defining sharp limits but it has been found that there are definite advantages to be obtained if the ethylbromide constitutes apreponderance, and preferably twothirds or more of the three-part compound. As much as about 5% of methylbromide is preferred, although half such amount is quite effective. An excess of 15% is not necessary in the composition and may increase the toxicity beyond reasonably permissible limits.

Each ingredient of the composition serves its particular purpose. Methylbromide is a particularly effective fire extinguisher. It is normally a heavy gas at temperatures above 4.5 degrees C. and efiectively blankets and extinguishes oil and gasoline fires. This gas, however, is highly toxic. By dilution, as with the ethylbromide present, its toxicity is reduced to within tolerable limits. Although the methylbromide present constitutes a minor proportion it is of major importance as an effective fire-extinguishing ingredient.

Ethylbromide has been discovered to possess good fire-extinguishing properties, especially in the composition described, although it is otherwise described in the literature. Boiling at 38 degrees C., it is a relatively heavy gas and particularly effective for extinguishing forced-draft oil and gas fires. The combination of low boiling point and high boiling point elements is considered to be decidedly better than either alone.

Ethylene chlorobromide is used in a relatively minor proportion. Having a boiling point of about 106 degrees, it brings down the vapor pressure of the mixture as a whole. Preferably the proportion present in the composition is sufficient to insure a vapor pressure of less than 25 pounds gauge at '70 degrees F. and therefore within the limits of I. C. C. Freight Tariff Rule 4. Low vapor pressure permits use of a less strong and lighter weight container.

When increasing the methylbromide content in order to improve the fire-extinguishing effectiveness, though at the expense of greater toxicity, the vapor pressure may be kept down by ineasing also the proportion or ethylenechloroamide. It is desirable especially for airplane res that a sufficient volume of the low boiling )int extinguishing gas be provided,

The preferred method of using compositions aving as principal effective ingredients the iemical compounds mentioned, or their equivants, respectively, involves applying fire-exnguishing liquid directly upon the burning lass. The fire-smothering gas or vapor will be :leased by the heat of the fire to extinguish the ewe. If the liquid be applied as a fine spray I. the forced draft evaporation is quicker and 1e action extremely efl'ective. The exact maner of the action of vapors to extinguish fire is at completely known but in some instances, at ast, the vapors evolving from the liquid prorcted on to the fire seem to envelop the mass of urning gas and carry it away without permitngthe flame to flash back to the combustible laterial.

In carefully conducted tests it has been estabshed that the mixture of vapors produced from me compositions described are particularly efiec- .ve for extinguishing fires of the type occurring 1 airplane power plants. At the same time the :xicity of the gaseous mixture is not beyond ermissible limits for the crew to endure.

The foregoing particular description is illusrative of the principles involved but is not inended as defining the limits of the invention. 'arious modifications and various other embodi aents may be developed without departing from he spirit of the invention aS defined in the ap- |ended claims.

What is claimed is:

1. The method of extinguishing fires which :omprises applying to the fire a liquid including LS its principal effective ingredients methylbromide, ethylbromide and ethylenechloro-' bromide in proportions approximating 4 to 10%. to and 10 to 20%, respectively, to produce fire-extinguishing vapors.

2, A vapor-forming fire-extinguishing liquid comprising as its principal efl'ective ingredients about '10 to ethylbromide, 5 to 10% methylbromide, and 5 to 20% ethylenechlorobromide. 3. A vapor-forming fire-extin liquid comprising as its principal effective ingredients minor proportions of methylbromide and ethylenechlorobromide and a major proportion of ethylbromide whereof the vapor pressure at 70 degrees F. is less than-25 pounds above atmospheric pressure.

4. Themethod of extinguishing fires which comprises applying to the fire a liquid containing 2 or more methvlbromide, a preponderance of ethylbromide and sufficient ethylene chloro bromide to reduce the vapor pressure of the composition at '70 degrees F. to about 25 pounds per square inch above atmospheric pressure.

5. The method of extinguishing a forced draft fire which comprises applying to the fire in the forced draft afine spray of a liquid including as principal efiective ingredients about 2/z% .or more methylbromide, about 4 to 10% ethylene chloro bromide and a major proportion of ethylbromide.

6. A vapor forming, fire-extinguishing liquid comprising as principal effective ingredients 2 to 15% methylbromide, a major proportion ethylbromide and sufiicient ethylene chloro bromide to reduce the vapor pressure at 70 degrees F. to less than 25 pounds per square inch above atmospheric pressure. LEWIS G. MORRIS TIMPSON. 

